[Gav]

Andrew,
I work with quite a few spraypainters and I am sure you will find that you will need to decide (I know its hard) who is going to paint your car.
Different paint brands require different prep products.
PPG will use a different type of primer to lets say House of Colour.
At the end of the day to reduce costs and prep time, your painter is going to want a particular base to work with. Talk with him and I'm sure he will not only specify what you want, but sell you the paint and give you loads of help too.